HEAT TRANSFER AUGMENTATION IN PLATE FINNED TUBE HEAT EXCHANGERS WITH VORTEX GENERATORS: A COMPARISON OF ROUND AND FLAT TUBES

Heat transfer augmentation and pressure loss penalty caused. by vortex generators (VGs) are numerically studied for finned flat/round tube heat exchangers and compared with available experimental results. The simulations are performed with the steady three-dimensional incompressible conditions and a RNG K-epsilon turbulence model is used. The Reynolds numbers based on the bulk velocity and the height of channel are selected from 600 to 4050. To compare the effectiveness of VGs on the round and flat tubes for tube-fin heat exchangers, two different configurations are investigated with two and four delta winglet vortex generators for each tube. The streamlines, vorticity, the averaged Nusselt number, the friction factor and the performance factor (JF) are provided to evaluate the effectiveness of VGs for the heat exchangers employed. It is found that the flat tube with VGs provides better thermal performance than the round one, especially at the lower Reynolds numbers.